Porous chemiluminescent material and method of manufacture

ABSTRACT

A POROUS SPONGE-LIKE CHAMILUMINESCENT MATERIAL COMPRISING POROUS POLYETHYLENE IMPREGNATED WITH TETRAKIS(DIMETHYLAMINO) ETHYLENE AND HAVING LITHIUM CHLORIDE DISPERSED THROUGHOUT THE WALLS OF THE PORES. THIS MATERIAL IS USED IN LOCATION MARKERS, FREE-FALL DISPENSERS, AND THE LIKE, AND GIVES GOOD LIGHT YIELD UNDER HUMID CONDITIONS.

A ril 24,1973

(3. A. HELLER ETAL POROUS CHEUILUMINESCENT MATERIAL AND METHOD OF MANUFACTURE Filed April 29. 1969 2 Sheets-Shem INVENTORS.

CARL A. HELLER HERBERT P. RICHTER WILLIAM 8. MC EWAN ROY MILLER ATTORNEY.

Apri 24, 1913 Q HE LER my. 3,129,425

POROUS CI'IEHILUMINESCENT MATERIAL AND METHOD OF'MANUFACTURE Filed April 29, 1969 2 Sheets-Sheet 2 I FORMULA 24 FORMULA 23 mwa ZMZDJ I XD E TIME-MINUTES '4 2 A I O S M 3 E T M M U 0 A I o W F L 2 M w E R 0 I m m P T 6 a 0 Z 4 2 I 6 4 2 S O. O O 0 O M G 0 0 0 0 I: E o o o F I- .rmumi .ru wwmzkImimm u0 u3m m R A 5 P S U G s R I E F V 4 T U P T G u ll 0 F T H m L I O O O O O 5 4 O 2 mmhj 1301 I ZUIDJ United States Patent O 3,729,425 POROUS CHEMILUMINESCENT MATERIAL AND METHOD OF MANUFACTURE Carl A. Heller, Herbert P. Richter, and William S. McEwan, China Lake, Califl, assignors to the United States of America as represented by the Secretary of the Navy Filed Apr. 29, 1969, Ser. No. 823,244 Int. Cl. C09k 3/00 US. Cl. 252-188.3 CL 3 Claims ABSTRACT OF THE DISCLOSURE A porous sponge-like chemiluminescent material comprising porous polyethylene impregnated with tetrakis- (dimethylamino)ethylene and having lithium chloride dispersed throughout the walls of the pores. This material is used in location markers, free-fall dispensers, and-the like, and gives good light yield under humid conditions.

GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The invention relates to a porous chemiluminescent material capable of improved light emission; more particularly, a chemiluminescent sponge comprising porous polyethylene saturated with tetrakis(dimethylamino)ethylene (TMAE) and lithium chloride dispersed throughout the walls of the pores.

Certain tetrakis(disubstituted-amino)ethylene compositions are known to luminesce when exposed to oxygen. Tetrakis(dimethylamino)ethylene has strong election donor properties and oxidizes vigorously in air with chemiluminescence. Kinetic studies have shown that the light producing reaction is complex and requires catalysis by protonic materials. The main oxidation products, tetramethylurea (TMU) and tetramethyloxamide (TMOA) act as quenchers for the light emission. The literature reports the following yield oxidation products of neat tetrakis- (dimethylamino)ethylene:formaldehyde, -4%; dimethylamine, 0-2%; tetramethylhydrazine; 510%; bis(dimethylamino)methane, 2-5%; tetramethylurea, 65-80%; and tetramethyloxamide, -20%. It is disclosed in copending patent application Ser. No. 803,526, filed Feb. 26, 1969', that a formulation containing powdered polyethylene, tetrakis(dimethylamino)ethylene and a powdered lithium halide gives superior light output apparently due to the lithium halide forming a complex with the tetramethylurea by-product thereby suppressing the light quenching effect caused by the excess tetramethylurea (TMU). The present invention is an improvement over said co-pending application. The powdered chemiluminescent formulation disclosed therein is operable when contained at a depth of approximately one centimeter. The powdered formulation is poorly effective alone, showing no beneficial effect of lithium chloride when spread thinly on a surface. The present new porous chemiluminescent material permits control of the duration or intensity of light by physical methods, and the material is effective in the field providing superior light output under various environmental circumstances including high humidity conditions.

It is the general purpose of this invention to provide a chemiluminescent material for use in nocturnal markers and signals over large areas which produce uniform light emission under varied climatic conditions when exposed to air. The material is particularly useful as a free-fall marker, and in large location markers to provide emer- 3,729,425 Patented Apr. 24, 1973 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded section of the material made in accordance with this invention;

FIG. 2 is a schematic illustration of the nature of the result of the dispersal of the nonporous powdered material having a similar formulation known to the art;

FIG. 3 is a schematic illustration of the nature of the result of the dispersal of the porous material made in accordance with this invention;

FIG. 4 is a graph showing a comparison of the performance of the material of this invention with a nonporous structure containing the same ingredients;

FIG. 5 is a graph showing a comparison of the performance in a field test of the present invention with a wax-based formulation containing tetrakis(dimethylamino)ethylene; and

FIG. 6 is a graph illustrating the relation of particle size of the present invention to light output.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1 there is shown a section of the porous chemiluminescent material, designated generally by numeral 14, made in accordance with this invention. Powdered polyethylene and sodium chloride were mixed together and heated until the polyethylene melted forming a mass which is cooled slightly before the sodium chloride is leached out with hot water leaving open pores 11 in the polyethylene. The porous polyethylene is now soaked in a methanol solution of lithium chloride. The methanol is removed by evaporation leaving fine lithium chloride crystals 12 dispersed throughout pores 11. The porous polyethylene containing lithium chloride is now saturated in an inert atmosphere with tetrakis(dimethylamino)ethylene forming the porous chemiluminescent material 31 which upon exposure to air luminesces or glows more intensely and for longer periods of time than the nonporous chemiluminescent materials.

In FIG. 2 there is shown how a nonporous powdered chemiluminescent material 15 when dropped from a freefall device in the field filters through the branches of a tree 16 creating little light output. FIG. 3 illustrates how strips of the porous material 14 of this invention hang onto the branches of a tree 17, or other shrubbery, thereby giving off an intense glow for a sustained duration of time.

The preferred formulation for the preparation of the present porous chemiluminescent material comprises a weight ratio for polyethylene, lithium chloride and tetrakis(dimethylamino)ethylene of 120.4: 1:5.

The following examples are given to illustrate the invention in greater detail.

Example I 800 grams of powdered sodium chloride and 200 grams of powdered polyethylene were mixed together and heated until all the polyethylene melted. The melt was cooled quickly so that the sodium chloride does not separate from the molten polyethylene. The sodium chloride is then leached from the cooled molten mass with hot water and the porous polyethylene is allowed to dry. A solution of lithium chloride was prepared by dissolving 300 grams of lithium chloride in a liter of methanol. The porous material cut into various sized particles or strips was next soaked in the solution of lithium chloride and the methanol was removed by evaporation leaving very fine crystals of lithium chloride dispersed throughout the pores of the polyethylene material. Water may also be used as a solvent for lithium chloride but requires a higher temperature in the solvent evaporation step. Strips of the sponge-like material were then packed into a dispensing type container. Tetrakis(dimethylamino)ethylene was poured into the container in sufficient amount to saturate the particles and the container was sealed. Several dispensers were made and tests of the material performed to determine the The flux and quantity of light does decrease with porosity decrease. The inventors at first used lower porosities in order to get a stronger particle to withstand explosive dissemination. However, it was found that 0.48 porosity material was no better than 0.71 porosity material in this light intensity and duration, also the dispersion pattern. respect. The results shown in FIGS. 4 and 5 present the The dispersion pattern was effected over a large area and marked improvement of the present porous material over the light emission intensity was beyond all expectation. nonporous powdered material and wax-based tetrakis(di- FIG. 4 compares a barely wet chemiluminescent powder methylamino)ethylene. Particles 5 mm.-round of 70% (non-porous material) containing polyethylene, lithium P y, 02415 111111- Pores and with Weight ratios f chloride, and tetra kis(dimethylamino)ethylene (desig- PEILiClITMAE equal to gave nated Formula 23) with the present porous material cellent field results. (designated Formula 24). Formula 24 shows superior light By th term large particle it is meant greater than the enhancement which is workable in the field Where it is p y at least the Wall thickness of h p By necessary to determine the location of military forces or p f It IS meant y Volume, C611 havlng Walls of to rescue personnel. varying thickness empty of solids or liquids during oxida- Example II j-h b d e porosity may e prepare in any fashion conl g polyethylene} g gga m venient so long as no material reactive with the tetrakisa ype 9 ymer ex a mlX re grams 0 (disubstituted-amino)ethylene is introduced. Cracks, sodium chloride and grams of powdered polyethylene. 20 fissures, and similar holes can all Work as pores 231:1 emlatreariaclilextvr'lutdhed intthe fsorn of roldls atd360 F t lilv The density of the product formed by this invention is leach d Y t c on e 1 en important since most devices in which it would be used 8 ou W1 0 wa er an yet y q are volume limited. There have been three kinds of density g gi g gi to f g g l g i 25 With these materials. First is the time density of the mam was prepare as escn e m Xamp terial without any pores. For example, the polyethylene and the Pmyethylene mds were soaked therem used was 0.916 21 m1. and sodium chloride was 2.165 and the methanol removed. by evahomtlon' The 3 g./ml. Both these materials are purchased as powders rous rods were cut into long sections and impregnated with with bulk densities of about ,0 467 and 125 g tetraklsmlmethylammq)ethylene under .inert conditiolts ml., respectively. The porous particles herein have appar- The .rods W stoled m alr'prpof contamers and used m ent densities that are the weight divided by external volspm'stablhzeq dlspenser h i dropped from the ume as measured geometrically. These apparent densities under Pumld atmosphenc q q (9.0% at may be as low as 0.2 g./ml.- Of course, these particles 2 i a of supenornensly dura' have a particle bulk density that depends upon how they i e 5 es 22% g? e an Otted 9 pack. Since the product of this invention is elastic it can 5 9 S i 1 f i i be packed tight by loading into a device with external pres- 0 Is mven.lon.( 0mm a a ase sure. It is also possible to raise the particle bulk density by Porous .ch?m11ummecent [formulation (Formula mixing particles of diiferent sizes so as to fill any voids The hthlum chlonde. crxstals do completely the (and incidentally to tailer the light duration). pores and the tetrakis(dimethylamino)ethylene is ab- 40 The weight ratio of tetrakiswimethylamino)ethylene sorbed into the polyethylene, but does not fill the pores, at lithium chloride, and polyethylene are important to the leashmt increase of light output. Lithium chloride with tetrakis Microscopic studies indicate that the lithium halide salt (dimethylaminokthylene overcomes the humidity prob dehquesces form t l m the Pores of the lem through the hygroscopic nature of this salt. The foam material. These lithium halide saturated pools of Serious quenching of light Output caused by the Oxidation water appaiently collect the tetramethylure"? oxldatlon by-product, tetramethylurea, is diminished due to its comproduct which is then complexed by the lithium halide. plexing with lithium chloride The pools of lithium halide salt Water throughout the Whatis claimedis. porous material thus act as microscopic reaction vessels The method for the Preparation of a porous n n for the removal of deleterious products from the chemiluluminescent material which comprises mlnesceht p heating a mixture of polyethylene and sodium chloride The slze of the Parhcles, S126 and total P 6 P to a temperature at which all the polyethylene melts centage volume aifect the duration and amount of light fo i a homogeneous mixture; output- These factors h he used to control the deshed leaching the sodium chloride from said mixture with hot P p of materfalexample, larger Parhcles water when the mixture has slightly cooled (forming show longer light duration above certain critical light inporous polyethylene; tensities as is presented in Table I below and in FIG. 6 soaking said porous polyethylene in a solution consistof the drawings. ing of lithium chloride in methanol;

TABLE I lParticlo size Test Concentrati d i T t 1Q F Time to b 011 77. max mat. Volume, 00 series Dimensions, mm. PE:LiCl:TMAE factor g eh lnii-fir-llm. min 177 1 x 5 x 5 wafer 1. 0:0. 61:0. 8 2.8 0. 35 14.3 56 15 37 101 1.5 irre ular 1.0:0.50:1.0 4.0 0.35 21.1 76 12.5 21 D-1 2 x 10 x 10 wafer 1. 0:0. 55:1. 0 2.8 0. 40 40. 6 68 30 70 202 3 long x 5 diam. cylinder" 1. 0:0. 5711. 0 5. s 0. 39 39.6 36 36 93 192 5 long x 5 diam. cylinder 1. 0:0. 58:1. 0 =4. 7 0. 35 40.3 56 27. 6 63 171 5x6x5cube 1.0:0.6l:0.87 6.0 0.35 39.5 60 32 66 173 10x10x10 cube 1. 0:0. 61:0. 87 6.0 0.35 31.4 65 27 50 Laboratory performance of Formula 24 as a function of particle size at 30 C. and

Duration to 1/10 of peak intensity.

Cylindrical particles lying on curved surface.

The integrated light output, Q, showed a definite in-- crease with particle size until maximum Q was reached with a minimum dimension 0t 2 to 5 mm. and a volume of approximately .1 cc.

R.H. Samples all of 0.70 porosity polyethylene.

evaporating the methanol from said solution leaving lithium chloride crystals dispersed throughout the pores of said polyethylene; and

saturating the resulting materials with tetrakis(dimeth- References Cited ylaminmethylene UNITED STATES PATENTS 2. A porous chemiluminescent material comprising polyethylene provided with a plurality of open pores 3,360,473 12/1957 252188-3 having walls of varying thickness; 5 Wmberg lithium chloride crystals dispersed throughout the walls 3,494,371 2/1970 PP et 252138-3 of said pores; and tetrakis (dimethylamino)ethylene soaked into said poly- CARL QUARFORTH Pnmary Examiner ethylene. P. A. NELSON, Assistant Examiner 3. The chemiluminescent material in accordance with 10 claim 2 wherein the ratio by weight of polyethylene, lith- U.S. C1.X.R.

ium chloride and tetrakis(dimethylamino)ethylene is about 1:0:0.4(+0.2) 1.50, respectively. 

